high electron mobility transistor hemt construction and the hemt or high electron mobility transistor is a type of field effect transistor fet that is used to offer a bination of low noise figure and very high levels of performance at microwave frequencies transistor a transistor is a semiconductor device used to amplify or switch electronic signals and electrical power it is posed of semiconductor material usually with at least three terminals for connection to an external circuit ma gallium nitride gan ma is driving the mercialization of gallium nitride into mainstream application by offering a portfolio of both gan on silicon si and gan on silicon carbide sic products